发表机构
The Australian National University; INAF - Osservatorio di Astrofisica e Scienza dello Spazio; Università degli Studi di Catania; Università degli Studi di Bologna; Vilnius University; INAF - Osservatorio Astrofisico di Arcetri（澳大利亚国立大学; 意大利国家天体物理研究所-天文与空间科学观测站; 卡塔尼亚大学; 博洛尼亚大学; 维尔纽斯大学; 意大利国家天体物理研究所-阿切特里天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用开普勒9,122颗巨星校准[C/N]-年龄-[Fe/H]关系，验证其在LRGB恒星中精度约30%，适用于[Fe/H]>-1，为光谱巡天提供有效年龄估计工具。
AI 中文摘要
[C/N]丰度比是巨星年龄的有力指示器，能够在传统方法受限的光谱样本中估算年龄。我们利用开普勒（Kepler）观测到的9,122颗巨星，结合星震学年龄和APOGEE DR17丰度，校准了一个多元的[C/N]-年龄-[Fe/H]关系。该校准分别针对下红巨星分支（LRGB）、上红巨星分支（URGB）和红团簇（RC）恒星进行。我们使用来自K2、TESS和疏散星团的独立样本验证了这些关系，发现与参考年龄吻合良好，尤其是对LRGB恒星，在约2-10 Gyr的年龄范围内，典型精度约为30%。对于URGB和RC恒星以及低金属丰度的情况，性能有所下降，这可能是由于额外的混合过程所致；对于年轻（<2 Gyr）和年老（>10 Gyr）的恒星，[C/N]-年龄相关性减弱。我们展示了基于[C/N]的年龄能够重现已知的银河系特征，包括[alpha/Fe]-[Fe/H]平面上的年龄分布以及银河系盘的膨胀。与其他化学时钟相比，[C/N]在其有效范围内提供了更稳健和精确的年龄估计。我们的结果表明，[C/N]结合金属丰度，是从光谱巡天中推导巨星年龄的有效经验工具，尤其适用于[Fe/H] > -1的LRGB恒星，使得银河考古学研究能够超越当前星震样本的覆盖范围。
英文摘要
The [C/N] abundance ratio is a powerful age indicator for giant stars, enabling age estimates for spectroscopic samples where traditional methods are limited. We calibrate a multivariate [C/N]-age-[Fe/H] relationship using 9,122 giant stars observed by Kepler, with asteroseismic ages and APOGEE DR17 abundances. The calibration is performed separately for lower red giant branch (LRGB), upper RGB (URGB), and red clump (RC) stars. We validate the relationships using independent samples from K2, TESS, and open clusters, finding good agreement with reference ages, particularly for LRGB stars, with typical precision of ~30% for ages between ~2 - 10 Gyr. The performance degrades for URGB and RC stars and low metallicities, likely due to extra mixing processes, for young (<2 Gyr) and old (>10 Gyr) stars, where the [C/N]-age correlation weakens. We show that the [C/N]-based ages reproduce known Milky Way features, including the age distribution across the [alpha/Fe]-[Fe/H] plane and the flaring of the Galactic disc. Compared to other chemical clocks, [C/N] provides more robust and precise age estimates within its domain of validity. Our results demonstrate that [C/N], combined with metallicity, is an effective empirical tool for deriving stellar ages of giant stars from spectroscopic surveys, particularly for LRGB stars with [Fe/H] > -1, enabling Galactic archaeology studies beyond the reach of current asteroseismic samples.
CommentsPaper accepted for publication in MNRAS
